Now has AGC for constant readings. No other equipment needed. Take it to your antenna site. Determine if your antenna is too long or too short, measure its resonant frequency, and its resistance to 500 ohms. It's the easiest, most
convenient way to determine antenna parameters. Resistance bridge, null meter, tunable oscillator-driver (1.8 to 30MHz). 9Vdc or 110Vac with MFJ-1312D. 7-1/2"H x 2-1/2"W x 2-1/4"D.